Eddy-current torque apparatus



Nov. 23, 1948. M. P. WiNTHER v 3 9 EDDY-CURRENT TORQUE APPARATUS 2 Sheets-Shani. 1

Filed Jan. 13, 1947 Nov 23, 1948.

M. P. WINTHER EDDY-CURRENT TORQUE APPARATUS Filed Jan. 13, 1947 TORQUE, POUND-INCHES v 20- 40. 6O 80 I00 I20 I40 I60 ISOZOO 23) 2 Sheets-Sheet 2 l ll 57" L57 4 WiTHOUT TORQUE CONTROL I 1 -waTH TORQUE CONTROL K34 H ;,..MM,LJ 5 :0 15202530354045505560 iNDUCTOR MEMBER SPEED RPM.

Patented Nov. 23, 1948 EDDY-CURRENT TORQUE APPARATUS Martin P. Wlnther, Waukegan, lll., assignor to Martin P. Winther, Waukegan, Ill., as trustee Application January 13, 1947, Serial No. 721,845 16 Claims. (01. 172-284) This invention relates to eddy-current torque apparatus and, more particularly, to constanttorque eddy-current brakes, slip couplings and the like.

Among the several objects of the invention may be noted the provision of an improved eddy-current torque apparatus for use as a brake, slip coupling or the like, adapted, when used as a brake, to provide a more constant braking torque characteristic upon a driven element and, when used as a slip coupling, to provide a more constant driving torque characteristic; the provision of apparatus of this class having a simplified automatic control which is responsive to applied torque; the provision of apparatus of this class for maintaining said characteristics over a wide range of speeds; and the provision of apparatus of this class which is simple in construction and reliable in operation, Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which several of various possible embodiments of the invention are illustrated,

Fig. 1 is a longitudinal section through the improved eddy-current apparatus of this invention, being taken on line l-l of Fig. 2 with parts being shown in elevation;

Fig. 2 is a fragmentary end elevation viewed from the right of Fig. 1 illustrating a torque-respcnsive control in one position of operation;

Fig; 3 is a view similar to Fig. 2, but illustrating the torque-responsive control in another (exaggerated) position of operation;

Fig. 4 is a diagrammatic view illustrating the application of the apparatus of Fig. l as a brake, and showing the electrical circuit therefor;

Fig. 5 is a diagrammatic view illustrating the application of the apparatus of Fig. 1 as a slip coupling, and showing the electrical circuit therefor; and,

Fig. 6 is a chart illustrating comparative torquespeed characteristics.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now more particularly to Figs. 1 -3, the eddy-current apparatus of this invention is shown to comprise relatively rotatable field and inductor members I and 3, respectively. Field member l comprises a drum 5 formed of magnetic material having an outwardly extending mounting flange 1 and an inwardly directed rim 9. Fitted within the drum is a field assembly comprising annular toothed rings H and I3 formed of magnetic material, and an annular field coil 15. Ring it is engaged against rim 9 with its teeth H extending axially toward the side of the drum opposite the rim. Annular coil I5 is disposed between teeth I! and the drum and is retained in position by ring l3, the teeth 19- of which extend axially toward the flanged side of the drum.- Teeth I1 and I9 are staggered and interflt, with spaces 20 therebetween. The entire assembly is retained within the drum 5 by welding 2|.

This arrangement is such as to provide an annular series of inwardly facing magnetic pole teeth, the inner pole faces of which define a cylindrical surface. When field coil i5 is energized, the effect is to establish an annular series of alternating north and south poles in a known manner (see for example U. S. Patent 2,212,192 and 2,401,- 187).

Inductor member 3 includes a discontinuous inductor ring 23 consisting of ring segments 25 formed of magnetic material and supported upon a hub 21 by resilient means permitting deflection of the segments relative to the hub similar to that disclosed in my copending application for eddycurrent coupling, Serial No. 693,057, filed August 26, 1946. Fixed on hub 21' in perpendicular planes are axially spaced, circular supporting plates 29 and 3 I A plurality of relatively thin, flexible fins 33 are secured to the peripheries of the plates.

Each fin comprises a flat, resilient metal strip normally disposed in a radial plane and extending radially outward from the peripheries of the plates. Each fin extends axially, spanning the plates, and is secured in aligned notches in the peripheries of plates 29 and 3| by welding or brazing 35, or the like. The ring segments 25 are secured to the radially outer ends of the fins by welding or brazing 31. They may be provided with copper eddy-current conducting ring segment 39 silver-brazed on the side faces of ring segments 25 for the purposes disclosed in my aforesaid copending application Serial No. 693,057.

The inductor member 3 is disposed within field member l in such manner that the outer faces of ring segments 25 normally lie in a cylindrical surface concentric with the cylindrical surface defined by the field pole faces with a small fluxtransmitting air gap 4| therebetween. When the field member I is excited by energizing its field coll IS, a toric flux field inductively is established masses interlinking the field member [1 and the inductor ring segments 25. This field is concentrated at the teeth H and E9 to form the said alternating north and south poles. Upon relative rotation of the field and the inductor ring segments 25, eddy currents are generated in the latter which produce a reactive magnetic flux field. The force due to the magnetic reaction. establishes a tangential drag between the field member I and the ring segments 25, tending to resist relative rotation of these elements.

Assuming that the inductor member 3 is rotating counterclockwise relative to the field member i, as viewed in Figs. 2 and 3 and as indicated by the arrow in Fig. 3, the tangential drag causes ring segments 25 to lag behind the hub Ti (and the plates 29 and ii fixed thereon) with resultant bending of fins 33 and inward deflection of segments 25, as illustrated in exaggerated fashion in Fig. 3. Fins 33 are sufllciently flexible to permit them to bend out of their radial planes to some extent due to the drag, the amount of deflection being substantially proportional to the drag.

Sufilcient space is provided between two adjacent fins 33a and 33b to accommodate a pressuresensitive variable resistor 43, preferably a variable carbon pile resistor. This resistor comprises a case 45 enclosing a pile of carbon discs and having an actuating knob 41 adapted to vary the pressure between the discs to vary the resistance of the pile. It will be understood that the re= sistance of the pile is in an inverse proportion to the pressure. The resistor is mounted upon the supporting plates 29 and BI in fixed relation with respect to the fin 3% by means of a bracket 49. The resistor is mounted in such position that its actuating knob extends rearward in relation to the direction of rotation of the inductor member relative to the field member.

radially (Fig. 2), finger i exerts maximum pressure upon actuating knob M and the resistance of resistor 13 is a minimum. When fin 33b flexes away from its radial plane under conditions wherein ring segments (including 25a) have lagged behind the hub 211 (Fig. a). finger 5i exerts less pressure upon the knob ill and the resistance of resistor 53 is accordingly increased. The resistor includes a knurled screw cap 52 for applying various initial pressures to the pile to provide for initial adjustments of its resistance.

Fig. 4 diagrammatically illustrates the application of the above-described eddy-current apparatus as a brake for applying a substantially constant braking torque upon a driven shaft 53. In this application of the apparatus, the field member I is ailixed to a stationary support 55 as by threading screws 56 through apertures in the mounting flange i into the support, or in any other suitable way. The inductor member is fixed upon the driven shaft 53 as by keying its hub 21 on the shaft. The field coil l5 of the field member I is connected in series with resistor 43 in a power circuit supplied by a suitable source of current, herein illustrated as a battery 51, under control of a switch 59. Connections to the resistor 43, which rotates with the inductor member 3, are made through collector rings El and 53 on hub 21, which cooperate with brushes 65 and 51, respectively. The negative terminal of the battery is connected by a line 59 including switch 59 to brush 65-. A wire ll connects collector ring 8i and one terminal it of the resistor 53. The other terminal M of the resistor is connected by a wire 1'! to collector ring 83. Line 18 -connects brush 6! and one terminal of the coil H5. The other terminal of the coil is connected to the positive terminal 0! the battery by a line M to complete the series circuit. 1

Operation oi. the above-described eddy-current brake is as follows:

Assume that the shaft 53 and the inductor member 3 are initially stationary and that switch 59 is closed so that field coil I5 is energized through resistor 43. Under these conditions, there is, of course, no tangential drag upon the ring segments lid. and the fin 38b is in its undefiected, substantially radial position of Fig. 2.

Finger 5i thus exerts maximum pressure on the actuating knob 4'! of resistor 43 and hence the resistance is at a minimum value. Maximum current therefore flows in the field coil i5 to establish a flux field of maximum strength.

Assume now that torque is applied to shaft 53 to rotate it counterclockwise, as viewed in Figs. 2 and 3, to bring it up to a given speed. As the inductor member 3 on the shaft rotates within the field member, a resisting tangential drag is applied to the inductor member. This drag is a function of (l) the strength of the flux field and (2) the speed of the inductor member. As the inductor member 3 increases in speed, the tangential dra'g increases until it is sufilclent to cause ring segment 25a to lag behind the hub and deflect fin 33?) away from its radial position of Fig. 2 to a position like that illustrated in Fig. 3. This condition is reached at the knee K of curve A illustrated in Fig. 6. This curve diagrammatically represents the torque-speed characteristic of the brake form of the invention. At speeds below this knee of the curve, the tangential drag is insufficient to cause enough deflection oi fin 33b to change the resistance much, and the curve A coincides with curve B. Thus up to point K the torque-speed characteristic is substantially the same as that of a brake such as herein disclosed but without the torque responsive field control. Adjustment of 52 controls the position of point K.

Upon deflection of the fin 33b away from its radial position, the pressure of finger St on knob M is decreased, the resistance of resistor 43 is increased, and the flow of current in field coil I5 is decreased to weaken the flux field. This momentarily decreases the tangential drag whereupon fin 33b momentarily returns towards its initial radial position. This again reduces the resistance of resistor l3 and causes more current to flow in field coil l5, thereby strengthening the fiux field and again momentarily increasing the drag. This action continues so that at a given speed the field current and the strength of the flux field are varied between maximum and minimum values. The maximum value cannot be higher than that which would be established at the given speed if the brake were not provided with the torque-responsive control resistor 43, and in fact is considerably lower. Hence the average value of the tangential drag and the resultant braking torque will be less than what it would be without the control. This average value is such as to provide a flatter speed-torque curve characteristic as illustrated by the curve A in Fig. 6. Without the control for resistor 43, the field strength would remain constant and the drag and torque would increase with increase in speed, as illustrated by curve B.

' such as to establish a braking torque which at the new higher speed is little if any higher than it was be ore. It will be understood that, upon reduction in speed of inductor member 3, the inverse of the above-described actions occur.

Thus, incipient change in torque upon ring 23,

' with change in ring speed, is utilized to actuate resistor 43 to control the energization of field member i to maintain a substantially more constant average braking torque.

Fig. diagrammatically illustrates the application of the apparatus of Figs. 1-3 as a slip coupling adapted to transmit constant driving torque from a driving shaft 83 to a driven shaft 85. In this application of the apparatus, field member 1 is afiixed to driving shaft 83 as, for example, by being secured to a disc 81 mounted upon the end of the shaft. Inductor member i is fixed upon the end of driven shaft 85 as by keying its hub on the shaft. The field coil i5 of the field member i is connected in series with resistor 43 in a power circuit similar in all respects to that disclosed in Fig, 4 except that sli ring conections 89 and 9! are introduced into lines 19 and 81 to supply field coil i5, which in the slip coupling embodiment rotates rather than being stationary.

Operation of the eddy-current slip coupling disclosed in Fig. 5 is as follows:

Assume that shaft 83 is being driven at a given speed and that switch 59 is closed to complete the circuit through the field coil i5 and resistor 43. Field member I is energized inductively to drive inductor member 3 in the same direction. This direction is clockwise, as viewed in Figs. 2 and 3. The inductor member 3 slips relative to the field member I, as is inherent in eddycurrent couplings of this class, so that the inductor member rotates counterclockwise relative to the field member as in the case of the brake,

and as indicated by the directional arrow in Fig. 3. The rate of slip, or slip speed, is determined by the extent of energization of field member I and the resultant fiux field strength. This, in turn, is determined by the pressure exerted by finger 5| of fin 33b on the actuating knob 41 of resistor 43 and the resultant resistance of the resistor. At the given speed of rotation of field member I and with the aforesaid fiux field strength, inductor member 3 is inductively driven to transmit a given driving torque.

Assume now that the speed of driving shaft 83 is increased. This increases the drag and the driving torque, inasmuch as it increases the slip speed which causes ring segment a. to rotate clockwise relative to hub 21, thereby deflecting fin 33b away from its radial position, and incipiently decreasing the pressure on knob 4'! of the resistor 43 to increase its resistance. This decreases the current flowing in the field coil i5 and weakens the flux field to decrease the drag which again causes fin 33b to move towards its radial position, decreasing the resistance and strengthening the field to increase the drag, and

. 6 so on. As in the case of the brake, the strength of the fiux field varies around an average value such as to maintain the driving torque more substantially constant than heretofore. It will be understood that, upon reduction of speed, the inverse of the above-described actions occur.

Thus, in the case of a slip coupling, incipient variations in driving torque exerted upon ring 23, with change in slip speed, are utilized to actuate the resistor 43 to control the energization of field member I to maintain substantially constant average driving torque at the output end of the drive.

The carbon pile resistor 43 is preferably one which requires very small range of movement of its actuating member 41 for control from maximum to minimum resistance. Such resistors are available and require no further description. It will be understood that instead of connecting the resistor directly in series with the field coil 15, the resistor may be in a separate sensitive electronic control circuit for the field coil circuit. The resistor, for example, might control the grid of a vacuum tube for controlling current flow in the field coil. It will also be understood that the resistance is also simply an example of one of several electrical means which might be mounted upon the driving member and controlled by the resilient member 5i thereon which might vary the flow of current in the circuit. For example. if alternating current were used, this resistor might be a reactance means.

Another point should be noted, namely, that the axis of the carbon pile of the resistor 43 is perpendicular to a radial line from the center of rotation of the member upon which it is mounted.

This prevents centrifugal forces from having any substantial effect upon the compression in the pile; whereas otherwise such centrifugal force would introduce a speed-responsive eifect, which is not desired.

A primary advantage of the eddy-current apparatus of this invention, either in its application as a brake Or a slip coupling, is that the control for varying the energization of the field member is directly responsive to incipient variations in torque rather than to changes in speed. Variation of the resistance of resistor 43 is caused by variations of the inductively applied torque resisting relative rotation of the field-and inductor members. Being directly responsive to torque, it quickly and accurately reflects variations in torque to vary the energization of the field to maintain the torque more constant than heretofore in comparable apparatus. This is advantageous since it is preferred in many instances to control braking or driving torque in accordance with variations in torque rather than in accordance with variations in speed.

It will be understood that the eddy-current apparatus of this invention also has all the advantages of the coupling described in my aforesaid copending application, Serial No. 693,057, such as the ability of the inductor ring segments to contract inward to prevent binding, low moment of inertia, etc.

It will be understood that the torque (braking torque in the case of the brake, drivingtorque in the case of the slip coupling) may be adjusted to various predetermined values by adjusting the knurled cap 52 of the resistor 43 to exert various initial pressures upon the carbon pile.

While Fig. 4 illustratesthe field member i as the stationary member, and the inductor member 3 as the rotatable braked member, it will be accuses t understood that this relationship may be reversed. Also, while Fig. illustrates the field member i as being the driving member and the inductor member 3 the driven member of the slip coupling, it will be understood that this relationship may be reversed.

In the following claims, the term driving member" means the member which receives energy for delivery into the apparatus. The term "driv-.

constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In apparatus of the class described, a driving member, a driven member, a field coil adapted to produce a fiux field interlinhing said members, the arrangement being such as to provide an inductive slip coupling between the driving and driven members whereby the driven member produces a reactive force upon the driving member, a circuit for said field coil, a control means in said circuit and mounted upon said driving member for movement therewith, a member resiliently mounted upon the driving member and responsive to said force to be deflected, and cooperative means between the resilient member and said control means such that force-induced deflection of the resilient means adjusts said control member to'control current to said coil in a manner causing incipient reduction in said force.

2. In apparatus of the class described, a rotary driving member, a rotary driven member, one

of said members having a relatively smooth eddycurrent portion and the other having flux-concentrating means opposite said eddy-current por tion, a field coil adapted to produce a flux field interlinking said members, the arrangement being such as to provide an inductive slip coupling between the driving and driven members whereby the driven member produces a reactive tangential force upon the driving member, said driving member having a deflectable portion responsive to said tangential force, a circuit for said field coil, a resistance in said circuit and mounted upon said driving member for movement therewith, said resistance being adapted to be changed by said deflectable member so as to reduce current in said coil according to deflection of said defiectable member in response to said tangential force, the action being such that variations in current due to variations in'the force cause the average value of said force at any speed to be lower than it would be without the resistance 3. In an eddy-current brake, slip coupling or the-like, relatively rotatable field and inductor members, the field member including a field coll,

- the inductor member comprising a discontinuous inductor ring including a plurality of ring segmerits mounted upon a hub by means of axially extending flexible fins, means for supplying cur-' rent to said field coil, and means responsive to flexing of one of said fins for varying said cur-.

rent.

4. In. an eddy-current brake, slip coupling or i the like, relatively rotatable field and inductorv lit members, the 'field member including a. field coll, the inductor member comprising a discontinuous inductor ring including a'plurality of ring segments mounted upon a hub by means of axially extending flexible fins, a variable resistor fixed on said hub and connected in series with said field coil, and means for varying the resistance of said resistor including one of said fins.

5. In an eddy-current brake, slip coupling or the like, relatively rotatable field and .inductor members, the field member including a field coil, the inductormember comprising a discontinuous inductor ring including a plurality of ring segments mounted upon a hub by means 01 axially extending flexible'fins, a pressure-sensitive variable resistor fixed on said hub and connected in series with said field coil, and an actuating member engaged by one of said fins for varying the pressure oil said resistor to vary its resistance upon flexing of said fin.

6. In an eddy-current brake, slip coupling or the like, relatively rotatable field and inductor members, the field member including a field coil,

means including a variable resistor for supplying current to said field coil to energize the field member and inductively to apply torque to the inductor member resisting relative rotation of said members, the inductor member comprising a hub, an inductive element in inductive relation to said field member, and means mounting said inductor element on the hub for rotation therewith and for limited .movement relative thereto upon incipient variations in said torque, and means responsive to relative movement of said inductor element and hub upon variations in torque for varying the resistance of said resistor and the energizatlon of said field member to control torque.. a

7. In an eddy-current brake, slip coupling or the like, relatively rotatable field and inductor members, means for energizing the field member inductively to apply torque to the inductor member resisting relative rotation of said members,

.members, the field member including afield coil, means including a variable resistor for supplying current to said field coil to energize the field member and inductively to apply torque to the inductor member resisting relative rotation of said members, the inductor member comprising a hub, an inductor element in inductive relation to said field member, means resiliently mounting said inductor element on the hub for rotation therewith and for limited rotation relative thereto upon incipient variations in torque, and means responsive to relative rotation of said inductor element and hub upon variations in torque for varying the resistance of said resistor and the energization of said field member to control said torque.

9. In an eddy-current brake,- slip coupling or the like, relatively rotatable field and inductor members, means for energizing the field member inductively to apply torque to the inductor member resisting relative rotation of said members. the inductor member comprising an inductor ring mounted on a hub by means of flexible members, said members being suificiently flexible to permit said ring to move relative to the hub upon incipient variations in said torque, with corresponding flexing oi said flexible members, and means responsive to flexing of one of said flexible members upon variations in torque for varying the energization of said field member to control said torque.

10. In an eddy-current brake, slip coupling or the like, relatively rotatable field and inductor members, the field member including a field coil, means including a variable resistor for supplying current to said field coil to energize the field member and inductively to apply torque to the inductor member resisting relative rotation of said members, the inductor member comprising an inductor ring mounted on a hub by means of flexible members, said members being sumciently flexible to permit said ring to move relative to the hub upon incipient variations in said torque, with corresponding flexing of said flexible members, and means responsive to flexing of one or said flexible members upon variations in torque for varying the resistance of said resistor and the energization of said field to control said torque.

11. In an eddy-current brake, slip coupling or the like, relativley rotatable field and inductor members, the field member including a field coil, means including a pressure-sensitive variable resistor for supplying current to said field coil to energize the field member and inductively to apply torque to the inductor member resisting relative rotation of said members, the inductor member comprising an inductor ring mounted on a hub by means of flexible members, said members being sufilciently flexible to permit said ring to move relative to the hub upon. incipient variations in said torque, with corresponding flexing 01- said flexible members, said resistor having an actuating member engaged by one of said flexible members for varying the pressure on said resistor and its resistance in response to incipient variations in said torque to control said torque.

12. An eddy -current brake comprising inductively related field and inductor members, one of said members being fixed and the other rotatable, the field member including a field coil, the inductor member comprising a discontinuous inductor ring including a plurality of ring segments mounted on a hub by means of axially extending flexible fins, a pressure-sensitive variable resistor fixed on said hub and connected in series in a power circuit with said field coil, said resistor having an actuating member engaged by one oi said flexible fins for varying the resistance of the re- 'sistor and the energization of the field member upon flexing of said fin in response to variations in torque to control said torque.

13. An eddy-current brake comprising a stationary annular field member having a field coil, an inductor member rotatable within said field member and comprising a discontinuous inductor iii connections wired to said resistor, said resistor including an. actuating member engaged by one of said flexible flns for varying the resistance of the resistor and the energization of the field member upon flexing of said fln in response to variations in torque to control said braking torque.

14. An eddy-current slip coupling comprising inductively related rotatable field and inductor members, one of said members constituting the driving member and the other the driven member of the coupling, the fleld member including a field coil, the inductor member comprising a discontinuous inductor ring including a plurality of ring segments mounted on a hub by means of axially extending flexible fins, a pressure-sensitive variable resistor fixed on said hub and connected in series in. a power circuit with said field coil, said resistor having an actuating member engaged by one of said flexible fins for varying the resistance oi the resistor and the energization of the field member upon flexing of said fin in response to variations in the torque transmitted by said coupling to control said torque.

15. An eddy-current slip coupling comprising a rotatable annular field member including a field coil, a rotatable inductor member within said field member comprising a'discontinuous inductor ring including a plurality of ring segments mounted on a hub by means of axially extending flexible fins, a pressure-sensitive resistor fixed on said hub and connected in series with said coil in apower circuit including slip-ring connections wired to said resistor and coil, said resistor including an actuating member engaged by one of said fins for varying the resistance of the resistor and the energization of the field member upon flexing of said fin in response to variations in the torque transmitted by said coupling to control said torque.

16. In apparatus of the class described, a driv-.

ing member, a driven member, afield coil adapted to produce a flux field interlinking said members, the arrangement being such as to provide an inductive slip coupling between the driving and the driven members whereby the driven member produces a reactive force upon the driving member, a circuit for said field coil. a control means in said circuit and mounted upon one of said members, an element forming a part of said lastnamed member and resiliently connected therewith and responsive to said force to be deflected, and cooperative means between the resilient element and said control means such that forceinduced deflection of the resilient element adjusts said control means to control current to said coil in-'a manner causing incipient reduction in. said force;

' MARTIN P. WINTHER.

REFERENCES CITED The following references are oirecord in the file or this patent:

UNITED STATES PATENTS Great Britain Aug. 6, 1931 

